The differential abilities of some molluscs to accumulate heavy metals within their shells in the Timsah and the Great Bitter lakes, Suez Canal, Egypt

The present study aims to investigate the different patterns of heavy metal bio-mineralization by some molluscs species (bivalves and gastropods) collected from the Timsah and Great Bitter lakes within their shells. Samples were collected from the two lakes, during the period from May 2016 to June 2017. The samples included seven mollusc species. The bio-available forms of the selected heavy metals: iron (Fe), manganese (Mn), Nickel (Ni), lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn), were determined in triplicates, using flame Atomic Absorption Spectrophotometer, then three individuals of each gastropod and bivalve species were selected for measuring heavy metals concentrations in their shells. Results showed that, the harvested (Fe) and (Mn) were the highest mineralized metals in the shell structures of the different species; while their bio-mineralization factor of metals (BMFM) ratios were significantly low. (Ni), (Pb) and (Cd) recorded the highest BMFM ratios; meanwhile, (Zn) and (Cu) showed significantly low BMFM in spite of their abundance in the mud fractions. The different species in the Timsah Lake had a BMFM of (<1.00). In the meantime, Brachidontes pharaonis harvested the highest BMFM where (2.36) was the value of (Cd); Cardium papyraceum procured the highest (Pb) (2.16) and Fusinus sp. showed the highest BMFM of (Ni) (1.10) in the Great Bitter Lake. The recorded variations in the BMFM ratios among the different species ascertain the probability of heavy metal mineralization selectivity depending on the local conditions much more than the heavy metals bioavailability.